1. Field of the Invention
The invention disclosed broadly relates to biasing and monitoring systems, and more particularly relates to biasing a field effect transistor ("FET") through the use of a look-up table to achieve optimal distortion levels despite a changing temperature.
2. Description of the Related Art
In typical circuits that require the biasing of a circuit element, the circuit is simply designed for a given temperature and the circuit elements are biased accordingly. The temperature that is designed for may be the preferred operating temperature, the worst case, or some other value. When the temperature fluctuates, however, the bias levels do not, and therefore the circuit might be performing sub-optimally much of the time. The same condition can occur for any circuit whose performance is dependent upon another variable, for example other environmental variables such as pressure and humidity, or circuit variables themselves, such as power, distortion, voltage, etc. The common problem is that for any given value of temperature (or some other variable), their is an optimal value for the bias level, but the bias level cannot be changed easily because the circuit design does not provide for it.
In circuits containing FETs, for example, it is desirable to bias each FET such that the intermodulation products are minimized. The proper value of drain-to-source current to achieve this minimization, however, is a function of the temperature. Thus, although the optimal current can always be determined, typical circuits are only designed to provide one value which corresponds to one temperature.
Accordingly, there is a need for a biasing and monitoring system which overcomes these problems.